Production of motor fuel



H. DIMMIG PRonUcTIoN oF MOTOR FUEL Filed Dec. 2v, 19:57`

Oct. 8, 1940.

. Patented ot.s,1`94o Gasoline Products Company, Inc., Newark. f

N. .Lucci-poration of Delay y 1 Application December 27,1937, serialV No. ranas( t sommi.` (Cireuse-,sml

. vThis invention relates to a `guethod for 'the production of gasoline motor-(fuel. More particularly, the. invention relates to a method for the simultaneous production of a gaseous mixture, containing la ysubstantial proportion of ethylene, and a gasoline motor :fuel of high antiknock value. v

Itis an object` ofthe .inventiontoprovide a method for converting pormallyliquid'hydro# carbons,'-particularly normally liquid hydrocarbons in the'gasoline boiling range, into normally gaseous hydrocarbons, including .a substantial proportion of ethylene, and normally yliquid hydrocarbons including a: gasoline fraction of extrernely` high anti-knockvalue. It is a further object ofthe invention to provide a vmethod for eifectng` the conversion of gasoline hydrocarbons of krelatively low anti-knock value to gasoline of high anti-knock value with the simultaneous prozo duction -of a gaseous mixtureincluding a `substantial'proportion of ethylene, under conditions ofmaximum efficiency. 4 In connection with the present invention it has been found that normall-yliquid hydrocarbons in the gasoline boiling range are most suitable-for the thermal productionof ethylene. `It hasbeen found," moreover, that the production of ethylene by this method also may 'be utilized to effect the production-'of a gasoline Amotor fuelhaving an extremely'high octane number, for example, 90 to vl0() C. F. R; M. It has been found also that the simultaneous production ofA motor fuel by this method makes possible more*` efficient and rapid production of ethylene.r f f In accordance 'with the present invention a gasoline, particularly one having v`a relatively low octane number, for example, a gasoline produced by the viscosity breaking of a heavier oil and having a gravity of 52 to 58 A. P. I. is, subjected, 40 in admixture with'a preponderant quantity of recycle gasoline, to relatively drastic 'cracking conditions of temperature and pressure to effect the production of gas and a gasoline product of improved anti-knock value. The cracked products are fractionated,fand the gaseous fraction consisting` essentially of propane Vand lighter gasesy and including a substantial proportion of ethylene, is Withdrawn .as ta product of the'process. `The cracked products are also fractionated to separate therefrom agasoline fraction which in the early stages of an voperation of `thellrocess is .returned substantially in itsventirety for reprocessing.' the gasoline. fraction so recovered constituting the` major portion ofthe hydrocar- 51 bon mixture undergoing cracking treatment, the

remaining minor portion consisting predominantly of gasolineccnstituents being introduced from an .external .source Vas the fresh .feedto the process. As-..thevoperation. proceedsl it is foundthat certain constituents of the fresh feed 5- or reaction products v of the. cracking. treatment are more refractory. and tend to-accumulate in the.; gasoliney being recirculated forreprocessing.

In connection withthe `presentinvention it .has been foundalsothat the A. P41; gravity ofthe 10 gasoline being recirculated decreases substantially..while the octane f number ofv ythis Y. material as gasoline motor fuel increases asv the 'gravity decreases. Atthe'same. time the rateL ofaproduction of gas, 'and therefore lthe rrateofvprol5 duction of ethylene,l decreasestasthe ,operation proceeds probably l, `due.Y sto. vthe accumulation.' of more refractory constituentsin the material/beingsubjected to the'crackingtreatmentj At the same time also the relativeproportionroffrelae 20 tivelyxed gasesl ofvinferior utility,=:suchfias methane, in the gaseous product is .increased,at the expense oi moredesired.productssuchas propylene. .It wouldappean .thereforefthat the Y cracking of ygasoline tof gases lincluding." ethylene 25 on a recycling basis results inthe accumulation,

or production and accumulation, inthe material ,being recycled of. a preponderanceof organic compounds which are relatively-refractory, 'rela-'- tively unsuited to the productionof valuablefgase- 30 ous products, and at the :same vtime constitute Vvaluable 'anti-knockingredients in Vconsidering the recycle Imaterial Vas a :gasoline motor. fuel, although it is to be` understood=1thattheinvention is not hunted by any such .theory in thisfresp'ect. 35

In accordance with the present invention',

therefore, the recycling fofsubstantially-.alliy the gasoline 'contained fin the.I Kcracked products iof the process is continued .until the A. P.` I." gravity of the recycledmaterial has been-substantially 40 reduced. Thereafter a' limited? proportion ofthe gasoline content of the yreactionproducts is withdrawn as a product off'theprocess. It 'is/found that thismaterial constitutes gasolineinotor fuel of vextremely vhigh octanel number` which i may be ,45 used in motors requiring the 5 use of fuel of -`this nature or may berusedfonblendingwith-:other fuels of lesser anti-knock value f The. inventionv will lbe described in detail: with specific referenceto the accompanying drawing. 50 The drawingis a diagrammaticviewL in elevation offone form of apparatus suitable for @carrying outthe process oftheinv'entiom Itwgislto be understood that the ydrawing and the. vfollowing specific descriptionwvith*referencefthereto 'are 55 merely for the purpose of illustrating an embodiment of the invention, the invention being capable of embodiments other than that illustrated.

The drawing illustrates apparatus for the treatment of a variety of hydrocarbon oils higher boiling than gasoline for the production therefrom of a gasoline suitable for further treatment in 'accordance with the present invention for the production of ethylene and a gasoline motor fuel of improved anti-knock value. In the apparatus illustrated in the drawing a heating coil I is provided for the heat treatment of an oil higher boiling than gasoline for the conversion thereof to gasoline. Coil I is heated by suitable conventional means not shown, and oil to be treated is introduced into the inlet of coil I by means of pipe 2 provided with a pump 3 for transferring the oil under treatment to form a source to be described below. In coil I the: oil under treatment is subjected to conditions of temperature and pressure suitable to effect conversion thereof to gasoline under conditions of maximum efficiency with respect to the production of gasoline and the inhibition of the formation of coke and gases. For example, a gas oil introduced through line 2 may be heated to a temperature of 850 to 1050" F. at a pressure of 100 to 500, or higher, pounds per square inch for a time sufficient to effect substantial conversion to gasoline with minimum production of gas and coke. The cracked products are withdrawn from coil I through line 4 and introduced thereby into an evaporator 5 wherein extremely high-boiling constituents undesired for recycling to the cracking operation are separated as liquid. If desired the cracked products may be cooled prior to introduction into evaporator 5 by indirect heat exchange or by admixture therewith of a cooling fluid. Means for effecting such cooling are not shown in the drawing, this operation being carried out by any suitable conventional means. The separation of the undesirable heavy material or tar in evaporator 5 may be promoted by cooling means, such as cooling coil 6 located in the top of evaporator 5.

The mixture of gases and vapors uncondensed in evaporator 5 is withdrawn therefrom overhead through line 'I and introduced thereby into a fractionator 8 wherein a fraction thereof higherv boiling than gasoline is separated as a liquid which collects in the bottom of fractionator 8. Cooling means such as cooling coil 9 may be provided in the upper part of fractionator 8 to effect the desired fractionation. Conditions in fractionator 8 are maintained to effect the passage overhead of a mixture of vapors and gases in which a major proportion of the normally liquid constituents are those within the gasoline boiling range. Preferably, the overhead from fractionator 8 should include substantially no constituents above the gasoline boiling range.

The fresh feed for the cracking operation carried out in coil I may be introduced to the system at a variety of places depending upon the character of the fresh feed. For example, a gas oil which does not contain constituents undesirably heavy for introduction into coil I at the inlet thereof may be introduced to the system through line I at the upper portion of fractionator 8. The introduction of such material in fractionator 8 serves to assist the fractionation desired and at the same time effects distillation and removal of any light constituents from the fresh feed which are suitable for inclusion in the mixture of gases and vapors passed over head from fractionator 8. The remainder of the unvaporized portion of the fresh feed collects in the bottom of fractionator 8 together with reflux condensate and is withdrawn therefrom through line 2 which, as described above, connects at its other end with the inlet of coil I.

If the fresh feed for the cracking operation in coil I is one including constituents undesirable for passage to the inlet of coil I, such as a heavy gas oil,a reduced crude,or a crude,it may be introduced into evaporator through line II whereby the incoming fresh feed is commingled with the hot cracked products from coil I and assists in the desired cooling of the latter. At the same time evaporation of constituents desired for charging to coil I and lighter constituents of the fresh feed is eiected in evaporator 5 by this means, and undesiredheavy ends are collected in evaporator 5 as liquid along with portions of the cracked products undesired for recycling. Depending on the nature of the fresh feed, some cracking of the latter may be effected at this point. By this method the constituents of the fresh feed suitable for passage to the inlet of coil I are collected in the bottom of fractionator 8 together with reflux condensate and lighter con-- stituents such as those within the gasoline boiling range and passed overhead in fractionator 8 together with the gasoline product of the cracking treatment in coil I.

Instead of or in addition to one or more of the methods described above for introducing the fresh feed to the system a heavy hydrocarbon oil such as a crude, or a reduced crude, or a. heavy gas oil may be introduced directly to coil I at one or more intermediate points thereof whereby the oil so introduced is subjected to relatively mild cracking conditions for a limited time in admixture with the lighter oil introduced into coil I at the inlet thereof, which has been cracked partially or substantially completely. Preferably, in accordance with this method the heavy oil is introduced at an intermediate point or points o'f coil I through line I2 whereby the said heavy oil passes only through that part of coil I located in a cooler portion of the furnace in which coil I is located. For example, the heavy oil may be passed through the soaking section of coil I. In this case some cracking of the fresh feed is effected in the coil, and the undesirable heavy constituents thereof and undesirably heavy products therefrom are collected in fractionator 5 as a -liquid along with similar undesirable high-boiling products of the cracking of the lighter oil introduced into coil I through line 2. By this method also gasoline produced by the cracking of the fresh feed, as well as by the cracking of the lighter oil treated in coil I, passes over head in fractionator 8, and reflux condensate from the said cracking operations collects in the bottom of fractionator 8 for passage to coil I through line 2.

The mixture of uncondensed vapors and gases passing overhead in fractionator 8 is withdrawn therefrom through line I3 which connects with a bubble tower or stabilizer Il wherein conditions of temperature and pressure are controlled to effect separation of light gases undesired for inclusion in the gasoline in the further treatment of the latter for the production of ethylene and high octane number gasoline motor fuel. To effect the desired separation cooling means such as cooling coil I5 and heating means such as heating coil I6 may be provided in the top and bottom, respectively, of bubble tower Il. Fractionation of the vapors and gases in bubble tower I4 preferably is controlled to effect passage overhead through line Il of a gaseous mixture consisting for the most part of propane and lighter gases, it being preferable to retain as much butane as possible in the liquid fraction.

With the operation of coil I under relatively high pressure it may be desirable to effect further treatment of the heavy liquid or tar collected in fractionator for recovery of constituents therefrom suitable for inclusion in the gasoline product inthe tower I4 or suitable for further cracking treatment in coll I. These liquids may be withdrawn from evaporator 5 through line I8 which connects with a flash tower I9. Line I8 is provided with a valve 20 for effecting the desired reduction in pressure. In flash tower I9 the vapors formed as a result of the reduction in pressure on the tar are fractionated to separate therefrom all constituents undesirably heavy for passage'with the reux condensate from fractionator 8 to the inlet of coil I for further cracking treatment therein. The mixture of unvaporized liquid and condensate from the vapors collects in the bottom of flash tower I9 and is withdrawn therefrom through line 2| for use elsewhere, for example, as fuel. The vapors uncondensed in flash tower I9 pass overhead through line 22 which is provided with a cooler 23 and connects with a separator 24. In the passage of the vapors through cooler 23 liquefaction of a. portion thereof is effected. Cooler 23 is operated to eect liquefaction of all constituents of the vapors in line 22 undesirably heavy for passage to tower I4 and inclusion in the gasoline co1- lected therein. In separator 24 the resulting mixture of vapors and condensate is separated. The uncondensed vapors are passed overhead from separator 24 through line 25 which connects with tower I4 and are introduced in tower I4 for treatment therein together with the vapors and gases introduced through line I3 as described above. The condensate separated in separator 24 is withdrawn therefrom through line 26 which is provided with a pump 21 and connects with the upper portion of fractionator 8 whereby this con-` densate-may be introduced into fractionator 8 for treatment therein together with materials introduced through line III and through line 1. If desired a portion of this condensate vmay be diverted from line 26 through line 28 which connects with the upper portion of ilash tower I9 for return of said portion to flash tower I9 as reflux to control the desired fractionation therein.

The gasoline collected as condensate in the bottom of bubble tower I4 is withdrawn therefrom through line 29 which connects with the inlet of a heating coil 30. Heating coil 30 is provided with any suitable conventional means for the application of heat thereto to raise the stream of material passing therethrough to substantially elevated temperature to effect conversion of constituents of said stream to gases containing a substantial proportion of ethylene and to gasoline constituents of improved anti-knock value.

The stream of gasoline supplied to the inlet of coil 38 from line 29 includes only a minor prof portion of gasoline withdrawn from bubble tower I4. The major portion of the stream consists of recycle gasoline introduced into line 29 from line 3| from a source described below. A pump 32 is located in line 29 between the connection thereof with line 3| and the inlet to coil 30 to e'ect the supply of the feed for heating coil 30 at the inlet thereof. The relative quantities of gasoline from bubble tower I4 and from line 3| supplied to coil 30 by pump 32 may be controlled by suitable manipulation of valves 33 and 34 located in lines 29 and 3|, respectively.

In coil 36 the gasoline stream passed therethrough may be heated under conditions suitable to effect the desired conversion. For example, the stream may be heated to a temperature of approximately 1000 to 1200 F. for a time sufficient to effect the desired conversion. Pressures may vary from atmospheric to substantially elevated pressures such as 500' pounds per square inch. Preferably, however, moderate pressures are employed in order to facilitate the formation ofv ethylene.

The conversion products from heating coil 30 are withdrawn. therefrom through line 35 which connects with an evaporator 36 wherein is effected separation of very heavy tar-like constituents from the gaseous and vaporous mixture of reaction products. This tar collects in the bottom of `evaporator 36 and is Withdrawn therefrom through line 31 for use elsewhere, for example, as fuel. If desired the conversion products in line 35 may be cooled prior to admission to evaporator 36. For example, a cooling uid from a source described below may be introduced through line 38 intoline 35. To promote the desired separation in evaporator 36 cooling means such as cooling coil 39 may be provided in the upper portion thereof.

The remaining mixture of gases and vapors, free of heavy tar-like constituents, passes overhead from evaporator 36 through line 40 which connects with a fractionator 4|. In fractionator 4| the mixture of gases and vapors is controlled to separate therefrom as a condensate hydrocarbons boiling above q the motor fuel boiling range. These hydrocarbonscollect in the lower portion of fractionator 4| and are withdrawn therefrom through line 38. Preferably, the heavy liquid withdrawn through line 38 is utilized for effecting cooling of the hot conversion products in line 35 as described above. At the same time contact of heavy oil with the hot conversion products effects cracking and conversion of the heavy oil with the production. of gases, gasoline constituents, recycle material and tar. The products of cracking of the heavier oil recycled through line 38 are separated in evaporator 38 and fractionator 4| along with the products of the cracking of gasoline in coil 30. A pump 42' may be provided in line 38 to eifect the transfer of thenheavy oil from the bottom of fractionator 4| for introduction into line 35. To eifect the desired fractionation in fractionator 4| cooling means such as cooling coil 43 may be provided in the upper portion thereof.

The gases and vapors uncondensed in fractionator 4| are withdrawn therefrom overhead through line 44 which connects with a bubble tower 45. In bubble tower 45 the mixture of gases and vapors introduced therein is fractionated to separate them into a liquid fraction including substantially all the gasoline constituents of the mixture and a gaseous fraction consisting essentially of propane and lighter gases including a substantial proportion of ethylene. The gaseous fraction is withdrawn from the upper portion of bubble tower45 as a product of the process through line 46. The gaseous'mixture withdrawn through line 46 contains a substantial proportion of ethylene and also may contain a substantial proportion of IpIOpylene. The gases may be employed in admixture for utilization of the ethylene content and other desired constituents thereof or may be subjected to fractionation by conventional means not shown to effect separation therefrom of the desired consti-tuents such as ethylene for use in a state purer than in the mixture of gases in line 46./ To effect the desired fractionation in bubble tower 45 cooling means such as cooling coil 41 and heating means such as heating coil 48 may be provided in the upper and lower lportions, respectively, of bubble tower 45.

The gasoline fraction is Withdrawn from the lower portion of bubble tower 45 through line 3| which connects, as described above, with line 29. Depending upon the stage of the operation all or a major proportion of the gasoline fraction from the bottom of bubble tower 45 is passed through line 3| into line 29 for admixture with a minor proportion of fresh feed from bubble tower I4 to form the stream of hydrocarbon material undergoing treatment in coil 30. Ordinarily, in the initial stage of the operation of the process substantially all the gasoline from bubble tower 45 is returned through line 3| for reprocessing in coil 30. After the operation has progressed for a time sufficient to effect a substantial decrease in the A. P. I. gravity of the gasoline separated in bubble tower 45 with a corresponding increase in its anti-knock value, a minor proportion thereof, for example, 2% to 10% by weight is continuously withdrawn from line 3| through line 49 as a product of the process, constituting a gasoline motor fuel of extremely high anti-knock value having an octane number of to 100 C. F. R. M. This product of the process may be used as motor fuel or may be used for blending with other motor fuels. Valve 50 is provided in line 49 for regulation of the withdrawal of the gasoline product of the process.

If the quantity of liquid condensate collected in bubble tower 4| and withdrawn therefrom through line 38 is insumcient to effect the desired cooling of the conversion product in line 35, a portion of the gasoline condensate from bubble tower 45 may be diverted from line 3| through line 5| which is provided with a valve 52 and connects with line 39 between pump 42 and fractionator 4|. Further conversion of the gasoline introduced into line 35 in this-manner may be effected by this means, but under ordinary conditions of operation the employment of the gasoline in line 5| in this manner is merely for the purpose of obtaining a cooling effect.

If the quantity of liquid condensate collected in bubble tower 4| is in excess of the amount required as cooling medium in line 35 the excess liquid may be diverted from line 38 through line 53 which is provided with a valve 54 and connects with line 26 whereby the said excess heavy liquid from fractionator 4| is passed to fractionator l to effect inclusion of the heavy portion of this liquid inthe reflux condensate collected in fractionator 8 and passed therefrom to heater through line 2.

The present invention provides an .efficient means for effecting conversion of gasoline constituents of low anti-knock value to gases containing substantial portions of ethylene and a rened gasoline product of extremely high antiknock value.

As a specific example vof the operation of that part of the process represented by heating coil 30, evaporator 36, fractionator 4|, and bubble tower 45, the gasoline condensate from bubble tower I4 may be admixed with recycle material through line 3| in an amount sufficient to supply the desired quantity of feed to the inlet of coil 30. At

the beginning of an operation of the process the quantity of gasoline from bubble tower I4 required to make up the dierence between the quantity of recycle material supplied through line 3| and the desired throughput for the coil 30 will be at a maximum. As the operation proceeds the quantity of recycle material available will increase for which reason the throughput to coil may be decreased to compensate for the lessened requirement of the gasoline product therefrom, or coil may be operated to supply the minimum amount of gasoline required, the excess required in the initial stages of the operation being supplied from storage by means not shown, or the coil may be operated to produce gasoline at a rate intermediate between the maximum and minimum amount required for coil 30, any excess being passed to storage by means not shown and returned to the system when the requirement for the supply to coil 30 exceeds the rate of production of gasoline by coil For example, in the initial stages of an operation of the process it may be found that enough gasoline from the bubble tower |4 is required to constitute 25% of the supply to the inlet of coil 30, but as the operation proceeds it may be found that this requirement decreases gradually -to approximately 15%. Thereafter as withdrawal of a portion of the gasoline condensate through line 49 as a product of the process is initiated the relative amount of `fresh feed in the mixture supplied to the inlet of coil 30 will be increased and may constitute 20% to 25% of the throughput in coil 30.

In treating gasoline produced by a viscosity breaking operation such as is illustrated in connection with coil the gasoline may be heated to a maximum temperature of 1200 F. in coll 39 with a reaction time above 1000 F. of approximately 9 to 10 seconds. The :pressure preferably is moderate. for example, about 50 pounds per square inch.

Separation of the products of the conversion operation in evaporator 36 is effected by maintaining a temperature in the upper portion of evaporator. of approximately 350 to 375 F. Fractionator 4| is operated with a top temperature of approximately 260 to 275 F. and a bottom temperature of approximately 325 to 335 F.

As the operation proceeds substantially all the gasoline withdrawn from fractionator 45 is passed through line 3| for introduction into line 29 lexcept that portion withdrawn for recirculation as.

cooling fluid through line 5|. As the operation proceeds the rate of production of gas decreases slightly, and the quality of the gas as regards unsaturates decreases although the proportion of ethylene therein remains substantially constant. The A. P. I. gravity of the gasoline withdrawn through line 3| decreases as the operationproceeds substantially below that of the fresh feed from bubble tower I4. For example, the gravity of the gasoline in line 3| may'delcrease gradually to a minimum of 38 to 40 A. P. I. as compared to a gravity for the fresh feed from tower I4 of approximately 55@ A. P. I. At the same time the gasoline in line 3| of the gravity mentioned will be found to have an extremely high octane number, for example, 90 to C. F. R. M. When this condition is reached, or prior to reaching this condition, in the operation it is desirable to initiate continuous withdrawal of a minor portion of the gasoline in line 3| from the system as a product of the process for use as motor fuel in operations requiring the extremely high anti-knock value of this mateto 20% etlrvlene.

. 2,217,588 rial or for blending. It is desirable to withdraw thereafter continuously from the system at line 49 2% to 10% by weight of the gasoline in line 3l, for example, 5%. Upon initiation of continuous withdrawal of the limited quantity of gasoline through line 49 the A. P. I. gravity of the gasoline inline 49 increases slowly to a iigure greater than the minimum to an extent depending upon the relative proportion of gasoline withdrawn through line 49. 'I'his is a matter of choice depending upon the operating conditions desired and the requirements on the process as to relativequantities of ethylene, etc., and gasoline desired as products. In order to maintain the production of gases at a desired rate it may be desirable to initiate withdrawal of gasoline from the system prior to the reduction of the A. P. I. gravity of the gasoline in line 3i to the.

extent mentioned above. However, in operating under the conditions mentioned above it will be found that after less than 100 hoursin operation the withdrawal of gasoline from the systemto the extent of approximately 4% by weight of that passing through line 3| may be initiated after which the operating conditions will become stabilized with the fresh feed constituting about 20% of the throughput of c`oil 30. Under these conditions the gravity of the gasoline withdrawn from the system will be stabilized at approximately 42 A. P. I., and this product of the process will have an octane number of approximately 92 to 95 C. F. R. M. The gas produced will be approximately 50% of the fresh feed and will be`over 50% unsaturated and will include 15% 'Instead of or in addition to gasoline from tower |4`, gasoline from other sourcesmay be treated. Foregexample, other gasoline obtained from conventionalgviscosity breaking operations or crude oil distillation may be treated in coil 30. Gasoline from these sources are ordinarily of low octane number and\admirably suited for treatment in accordance with the process of the invention. l

'The present invention has been described with reference to a specific embodiment illustrated in the drawing and to the specific example. It is to be understood, however, that the invention is not limited by such specinc description but is capable of other modifications than that illustrated and described.

I claim:

1. The method of producing simultaneously gasoline of high anti-knock value and an ethylene-rich gas which comprises heating a hydrocarbon mixture consisting of a minor portion of a gasoline of low anti-knock value introduced into the process as fresh feed and at least of a recycle gasoline having a C. ER. M. octane number not substantially lower than from a source described belowto eil'ect conversion of constituents of said mixture togasoline constituents of high anti-knock value and. hydrocarbon gases, separating from the conversion products the gasoline content thereof and an ethylenerich gas "fraction, separating the gasoline thus recovered from the conversion products prior to admixture therewith of gasoline from an external source into a major fraction and a minor fraction having approximately the same boiling characteristics, said minor fraction constituting 2 to 10% by weight of the gasoline content of the conversion products, withdrawing the minor fraction as a product of the process, and incorporating the major fraction in the first-mentioned gasoline hydrocarbon mixture for further conversion treatment therein as a substantial constituent portion thereof.

2. The method of producing simultaneously gasoline of high anti-knock value and an ethylene-rich gas which comprises heating a hydrocarbon mixture consisting of a minor portion of a gasoline of low anti-knock value introduced into the process as fresh feed and at least 75% of a recycle gasoline having a C. F. R. M. octane number not substantially lower than 90 from a source described below to eil'ect conversion of constituents of said mixture to gasoline constituents of high anti-knock value and hydrocarbon gases, separating from the conversion products the gasoline content thereof and an ethylenerich gas fraction, continuously recycling substantially all of the gasoline thus recovered from the conversion products by incorporation thereof in the first-mentioned gasolinehydrocarbon mixture for further conversion treatment therein as a substantial constituent portion thereof, continuing said recycling of substantially all said gasoline content of the conversion products until the A. P. I. gravity of said gasoline has been substantially reduced, thereafter separating the gasoline content of the conversion products prior to admixture therewith of gasoline from an external source into a minor fraction and a major fraction having approximately the same boiling characteristics, said minor fraction constituting 2,to 10% by weight of the said gasoline content of the conversion products, withdrawing the minor fraction as a product of the process, and continuously f recycling the maior fraction as described.

3. The method in accordance with claim 2 wherein recycling of substantially all the gasoline content of the conversion products is continued until the gravity of said gasoline has been reduced to approximately 40 A. P. I.

4. The method of producing simultaneously a gasoline of high anti-knock value and an ethylene-rich gas which comprises heating a hydrocarbon mixture consisting of a minor portion of a gasoline of low anti-knock value introduced to the process as fresh feed and at least 75% of a recycle gasoline having a C. Il'. R. M. octane number not substantially lower than 90 from a source described below to eifect conversion oi' constituents of said mixture to gasoline constituents of high anti-knock value and hydrocarbon gases, separating from the conversion products the gasoline content thereof and an ethylenerich gas fraction, separating the gasoline thus recovered from the conversion products prior to admixture therewith of gasoline from an external source into a minor fraction and a major fractiony having approximately the same boiling characteristics, said minor fraction constituting .o

approximately 5% by weight of the gasoline content of the conversion products. withdrawing the minor fraction as a product of the process, and recycling the major fraction for admixture with gasoline of low anti-knock value introduced as fresh feed to the system for further conversion treatment.

5. The method of producing simultaneously a gasoline of high anti-knock value and an ethylene-rich gas which comprises heating a hydrocarbon mixture consisting of a minor portion of gasoline of low anti-knock value introduced into the process as fresh feed and at least '15% of 'a recycle gasoline having a C. F. R. M. octane number not substantially lower than 90 from a source described below to effect conversion of constituents of said mixture to gasoline constituents of higher anti-knock value and hydrocarbon gases, admixing with the conversion products a. cooling liquid predominating in hydrocarbons boiling above the gasoline boiling range, fractionating the conversion products and accompanying cooling liquid'to separate therefrom an ethylene-rich gas fraction, a high-boiling normally liquid fraction boiling above the gasoline boiling range, and a gasoline fraction consisting oi the gasoline content oi.' the said conversion treatment, admixing with said conversion products as a cooling liquid at least a portion of said high-boiling normally liquid fraction, separating said gasoline fraction of the conversion products prior to admixture therewith oi' gasoline from anu external source into a minor .fraction and a major fraction having approximately the same boiling characteristics, said minor fraction constituting 2 to 10% by weight of said gasoline fraction, withdrawing the minor fraction as a product of the process, and recycling the major fraction for incorporation in said first-mentioned gasoline hydrocarbon mixture for further conversion treatment therein as a substantial constituent portion thereof.

6. The method of producing simultaneously a gasoline of high anti-knock value and an ethylene-rich gas which comprises heating a hydrocarbon mixture consisting of a minor portion oi' gasoline of low anti-knock value introduced as fresh feed to the process and at least 75% of recycle gasoline having a C. F. R. M. octane number not substantially lower than 90 from a source described below to a temperature oi'approximately 1000 to 1200 F. to effect conver-` the gasoline content of theV conversion products prior to admixture therewith o1' gasoline from an external source into a minor fraction and a major fraction having approximately the same boiling characteristics, said minor fraction constituting 2 to 10% by weight of the gasoline content of the conversion products, withdrawing the minor fraction as a product of the process, and recycling the maior traction for admixture with gasoline of low anti-knock value as described.

HOWARD DIMMIG. 

